Step 1: Find and Prepare the Form

I found these nested egg forms at a local department store for about $13 (see Walmart link below). There is about a 3/4" space between sizes, which is ideal for the amount of GIY material being used and to ensure there is a strong wall when the parts are finished. I used some isopropyl alcohol in a spray bottle to make ensure the forms were clean and wouldn't grow any contamination.

Step 3: Fill the Forms

I filled the forms in two halves, so that I could remove the plastic form from the inside before growing the two halves together. Be sure to pack the material in all the way to the bottom. Once the material is filled to the top I covered the entire thing with Seran wrap and poked several holes in the top with a thumb tack to allow the mushrooms to breath. I also poked a few holes in each of the plastic eggs to allow for additional breathing.

Step 4: Let It Grow!

After about 24 hours of growing the GIY material should be grown together enough to mostly hold its shape and pull the plastic mold off. After pulling the parts out place them in a plastic bag and attach the two halves together with toothpicks. This will provide some additional support to allow the parts to grow together at the seam. Allow the parts to grow for an additional 24 hours.

Step 5: Drying

To dry the parts, place in a conventional oven at 180F for 2-3 hours. If that isn't an option, the parts can be placed out in a dry location for 24 hours with a small fan blowing air over them.